Conduit intersection for high pressure fluid flow

ABSTRACT

A body ( 30 ) having a conduit ( 38 ) adapted for fluid flow under high pressure includes a first passageway ( 32 ) having a first longitudinal ( 33 ) axis and second passageway ( 34 ) having a second longitudinal axis ( 35 ). The first and second longitudinal axes intersect each other at an angle. An enlarged generally spherical cavity ( 36 ) having a center point ( 42 ) at the intersection of the first and second longitudinal axes reduces stress on the walls of the conduit. Particular application is found in a fuel distribution system for an internal combustion engine.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to metal bodies with conduits forhigh-pressure fluid flow. More particularly, the invention relates toangular intersections of high-pressure fluid flow conduits.

2. Description of the Related Art

Various applications utilize conduits in metal bodies for fluid flowunder high pressure. Often those conduits comprise two or morepassageways that are angled with respect to one another. For example,fuel distribution systems with fuel injectors are employed in internalcombustion engines for delivering a predetermined, metered amount offuel to the combustion chamber at preselected intervals. In the case ofcompression ignition, or diesel engines, the fuel is injected into thecombustion chamber at relatively high pressures. Presently, conventionalinjectors are delivering this fuel at pressures on the order of 29,000psi (2,000 bar). Often the conduits for delivery of fuel under pressurehave one or more turns so that the passageways in the conduit are angledwith respect to one another.

Illustrations of the intersections such conduits may employ are seen inFIGS. 1-3 a. Looking first at FIG. 1, for example, a metal body 10 haswithin it a conduit 12 comprising a first passageway 14 and a secondpassageway 16. The first and second passageways 14, 16 are at an anglewith respect to each other, forming an elbow intersection 18. Theconduit 12 is typically formed by drilling into the body 10 to form eachpassageway 14, 16 and to form the intersection 18 where the passagewaysmeet. Natural consequences of this operation at the intersection 18include sharp corners and burrs. Thus, a second operation will normallyuse electrochemical machining (ECM) to smooth and blend the passageways14, 16 at the intersection 18, typically resulting in a radius 20 at theinside angle and a radius 22 at the outside angle of the intersection18. FIG. 2 shows a conduit 12 with an intersection 18 similar to that ofFIG. 1, except that the angle between the passageways 14, 16 is closerto 90°. In FIG. 3, a T-intersection 18 between passageways 14, 16provides two inside radiuses 24, 26.

It will be understood that a cross section of a passageway is normallycircular. However, it can be seen in FIGS. 1 a, 2 a and 3 a that a crosssection taken at the intersection 18 is not circular, but elliptical.Generally, the more acute the inside angle between two passageways 14,16, the more elongated the elliptical cross section at the intersection18. A known problem at such intersections is the failure of the body 10resulting from the high pressures induced by fluid. Such failures areevidenced by cracks that form at inside radiuses 20, 24, 26. It isbelieved that such failures are due to uneven distribution of stress dueto fluid pressure against the conduit wall at the intersection where thecross-sectional area is not circular. Finite element analysis of atypical case has shown stresses on an inside radius at a 90°intersection with fluid pressures of 29,000 psi (2000 bar) as high as850 MPa or 123 KSI.

Such failures become even more critical in fuel injectors as increasingdemands on greater fuel economy, cleaner burning, fewer emissions, andNO_(x) controls have placed, and will continue to place, even higherdemands on the engine's fuel delivery system including increasing thefuel pressure within the injector.

There is a need for a solution to the problems arising from angledintersections in high-pressure fluid flow conduits. One obvious solutionis to design bodies without angled intersections. However, size andweight in designs utilizing high pressure conduits without angles oftencome at a high cost, rendering them commercially unviable.

SUMMARY OF THE INVENTION

A solution to these and other problems is found in an improvement forany body with a high-pressure fluid conduit formed of a first passagewayhaving a first longitudinal axis and second passageway having a secondlongitudinal axis, where the first and second longitudinal axesintersect at an angle other than 180 degrees. The improvement lies in anenlarged cavity having a center point at the intersection of the firstand second longitudinal axes.

Preferably the enlarged cavity is generally spherically shaped, and thediameter of the cavity is at least twice the cross sectional diameter ofone of the first and second passageways. In one aspect, the anglebetween the first and second passageways is about 90 degrees.

In another aspect of the invention, a method is described formanufacturing a body having a conduit with a first passageway having afirst longitudinal axis and second passageway having a secondlongitudinal axis, where the first and second longitudinal axesintersect at an angle other than 180 degrees. The conduit also has anenlarged cavity having a center point at the intersection of the firstand second longitudinal axes. The method includes the steps of drillingthe first passageway into the body along a first longitudinal axis,drilling the second passageway into the body along the secondlongitudinal axis until the second longitudinal axis intersects thefirst longitudinal axis, and then utilizing electromechanical machiningto remove material from the walls of the first and second passagewaysadjacent the intersection of the first and second longitudinal axesuntil the enlarged cavity is formed with a center point at theintersection.

Preferably, the step of utilizing electromechanical machining includesremoving material evenly in all directions to form a spherical cavity.Also, material can be removed in all directions until the diameter ofthe cavity is at least twice the diameter of the first or the secondpassageway.

The invention has particular applicability in the field of fueldistribution systems for fuel injectors.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional side view of a prior art high-pressureconduit in a body.

FIG. 1 a is a cross sectional view of the conduit of FIG. 1 taken alonglines 1 a-1 a.

FIG. 2 is a cross sectional side view similar to FIG. 1 of anotherembodiment of a prior art high-pressure conduit in a body.

FIG. 2 a is a cross sectional view of the conduit of FIG. 2 taken alonglines 2 a-2 a.

FIG. 3 is a cross sectional side view similar to FIGS. 1 and 2 of thirdembodiment of a prior art high-pressure conduit in a body.

FIG. 3 a is a cross sectional view of the conduit of FIG. 3 taken alonglines 3 a-3 a.

FIG. 4 is a cross sectional side view of a high-pressure conduit in abody according to the invention.

FIG. 4 a is a cross sectional view of the conduit of FIG. 4 taken alonglines 4 a-4 a.

FIG. 5 is a cross sectional side view similar to FIG. 4 of anotherembodiment of a high-pressure conduit in a body according to theinvention.

FIG. 5 a is a cross sectional view of the conduit of FIG. 5 taken alonglines 5 a-5 a.

FIG. 6 is a cross sectional side view similar to FIGS. 4 and 5 of athird embodiment of a high-pressure conduit in a body according to theinvention.

FIG. 6 a is a cross sectional view of the conduit of FIG. 6 taken alonglines 6 a-6 a.

FIG. 7 is a schematic view of a fuel distribution system with ahigh-pressure conduit according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Looking first at FIGS. 4 and 4 a, a metal body 30 has drilled into it afirst passageway 32 with a longitudinal axis 33 and a second passageway34 with a longitudinal axis 35 at an angle α relative to each other.Preferably, the passageways 32, 34 will have the same cross-sectionaldiameter, although it is not essential to the invention. Typically theangle α will be between 90° and 180°. Each passageway 32, 34 fluidlyconnects to an enlarged cavity 36, defining an intersection between thetwo passageways, and establishing a conduit 38 through the body 30. Thecavity 36 is enlarged in the sense that any measure of its cross sectionwill be larger than a cross sectional diameter of an adjacent passageway32, 34. Preferably, the cavity 36 is generally spherical. There may ormay not be a radius at the junction of a passageway 32 or 34 and thewall of the cavity 36. Thus, a cross sectional view of the body at thecavity 36 is shown as roughly circular in FIG. 4 a with a smallerdiameter opening 40 to the passageway 34.

Formation of the cavity 36 can be obtained by utilizing the same ECMprocess used to generate a radius at the intersection of passageways inhigh-pressure fluid conduits of the prior art. Currently, ECM removesmaterial selectively where a radius is desired. To generate a cavityaccording to the invention, ECM is used to remove material at theintersection in all directions, thereby generating a roughly sphericalcavity. It is believed that the more spherical the cavity, the moreevenly stresses introduced by fluid under high pressure are distributedat the intersection. Also, the larger the cavity, the lower the stressesat the intersection. Consequently, there is less likelihood of stressfailures occurring at the intersection.

The cavity 36 need not be spherical. It is important that the geometryof the cavity represent roughly the cross section of a passageway 32, 34at any angle. Also, the center 42 of the cavity 36 should be located atthe intersection of the longitudinal axes 33, 35. Thus the opening 40 ofpassageway 34 will remain circular as if it were breaking into aperpendicular plane. Likewise the opening 44 of the passageways 32 willalso be circular at its junction with the cavity 36. Preferably thediameter of the cavity 36 will be at least twice the cross sectionaldiameter of the passageways 32, 34.

The benefits of the invention are even more apparent when the angle Caapproaches 90° as illustrated in the embodiment of FIGS. 5 and 5 a. Herecomponents identical to those of FIGS. 4 and 4 a are shown with likenumerals. In fact, the only difference between the embodiment of FIG. 4and that of FIG. 5 is the measure of the angle α. Finite elementanalysis on a roughly 90° intersection with a spherical cavity accordingto the invention (as shown in FIG. 5) at a fluid pressure of 29,000 psi(2000 bar) shows generally uniform stress on the walls of the cavity at550 MPa or 80 KSI, a reduction of over 35% from the stresses projectedin a comparable prior art blended intersection with only radiusesbetween the passageways (as shown in FIG. 2).

FIGS. 6 and 6 a illustrate a conduit 48 with a T-intersection accordingto the invention. Here a first passageway 50 has a longitudinal axis 52and a second passageway 54 has a longitudinal axis 56 at roughly a 90°angle to the first passageway. A spherical cavity 58 has a center point60 located at the intersection of the longitudinal axes 52, 56. Thus thepassageways present three openings 62, 64, and 66 to the cavity 58establishing the conduit 68. As explained earlier, the diameter of thecavity 58 is roughly (although not necessarily) twice the diameter ofany cross section of a passageway 50, or 54. It is observed that whenfluid under high pressure is introduced in the conduit 68, stresses onthe wall of the cavity 58 are more evenly distributed and lower thanthey would be in a comparable radiused intersection without a cavity.

Looking now at FIG. 7, an embodiment of a high-pressure fueldistribution system 100 incorporating a high-pressure fuel conduitaccording to the invention is shown. The fuel distribution system 100 isone that might typically be found on a diesel engine, for example. Thesystem comprises generally a fuel pump 102 and a fuel injector 104. Thefuel pump pressurizes the fuel as it is delivered to the injector 104,and when triggered to do so in the engine cycle, the injector releasesthe pressurized fuel into a combustion chamber. Delivery of the fuelunder high pressure from the pump 102 to the injector 104 is through abody 106 having a high-pressure fuel conduit generally indicated at 108.The high pressure fuel conduit 108 may be formed by drilling a pair ofholes; one starting at one side of the body 106 to form a firstpassageway 110 having a longitudinal axis 112, and another beginningfrom another side of the body 106 to form a second passageway 114 havinga longitudinal axis 116 which meets the first drill hole at an elbow118. The longitudinal axes 112, 116 intersect at an angle other then180°. In accord with the invention as shown above in FIGS. 4 and 4 a,the elbow 118 is enlarged by ECM to form an enlarged cavity 120,preferably spherical. The center point 122 of the cavity is at theintersection of the longitudinal axes 112, 116 of the first and secondpassageways 110, 114. When fuel under high pressure moves through theconduit, the stresses exerted on the walls of the cavity 120 by the fuelpressure are not high enough to cause stress fractures in the body 106.

While the invention has been specifically described in connection withcertain specific embodiments thereof, it is to be understood that thisis by way of illustration and not of limitation, and the scope of theappended claims should be construed as broadly as the prior art willpermit.

1. In a body having a conduit formed of a first passageway having afirst longitudinal axis and a second passageway having a secondlongitudinal axis wherein the first and second longitudinal axesintersect at an angle other than 180 degrees, the improvementcharacterized by: an enlarged cavity having a center point at theintersection of the first and second longitudinal axes.
 2. Theimprovement of claim 1 wherein the enlarged cavity is generallyspherically shaped.
 3. The improvement of claim 2 wherein the diameterof the enlarged cavity is at least twice the cross sectional diameter ofone of the first and second passageways.
 4. The improvement of claim 1wherein the angle is about 90 degrees.
 5. The improvement of claim 4wherein the diameter of the enlarged cavity is at least twice the crosssectional diameter of one of the first and second passageways.
 6. Amethod of manufacturing a body having a conduit with a first passagewayhaving a first longitudinal axis and second passageway having a secondlongitudinal axis wherein the first and second longitudinal axesintersect at an angle other than 180 degrees, and an enlarged cavityhaving a center point at the intersection of the first and secondlongitudinal axes, comprising the steps of: drilling the firstpassageway into the body along a first longitudinal axis; drilling thesecond passageway into the body along the second longitudinal axis untilthe second longitudinal axis intersects the first longitudinal axis;utilizing electromechanical machining to remove material from the wallsof the first and second passageways adjacent the intersection of thefirst and second longitudinal axes until the enlarged cavity with acenter point at the intersection is formed.
 7. The method of claim 6wherein the step of utilizing electromechanical machining includesremoving material evenly in all directions to form a spherical cavity.8. The method of claim 7 further comprising removing material in alldirections until the diameter of the cavity is twice the diameter of oneof the first and second passageways.
 9. A fuel distribution system foran internal combustion engine comprising: a pump; an injector; a fuelconduit in a body, fluidly connecting the pump to the injector, saidfuel conduit being adapted for delivery of fuel at high pressure, havinga first passageway with a first longitudinal axis and a secondpassageway with a second longitudinal axis wherein the first and secondlongitudinal axes intersect at an angle other than 180 degrees; and anenlarged cavity having a center point at an intersection of the firstand second longitudinal axes.
 10. The fuel distribution system of claim9 wherein the enlarged cavity is generally spherically shaped.
 11. Thefuel distribution system of claim 10 wherein the diameter of theenlarged cavity is at least twice the cross sectional diameter of one ofthe first and second passageways.
 12. The fuel distribution system ofclaim 11 wherein the angle is about 90 degrees.
 13. The fueldistribution system of claim 9 wherein the diameter of the enlargedcavity is at least twice the cross sectional diameter of one of thefirst and second passageways.
 14. A unit fuel injector for an internalcombustion engine, the unit fuel injector being of the type comprising apump, an injector, and a body, characterized by: a fuel conduit in thebody, fluidly connecting the pump to the injector, said fuel conduitbeing adapted for delivery of fuel at high pressure, having a firstpassageway with a first longitudinal axis and a second passageway with asecond longitudinal axis wherein the first and second longitudinal axesintersect at an angle other than 180 degrees; and an enlarged cavityhaving a center point at an intersection of the first and secondlongitudinal axes.
 15. The unit fuel injector of claim 14 wherein theenlarged cavity is generally spherically shaped.
 16. The unit fuelinjector of claim 15 wherein the diameter of the enlarged cavity is atleast twice the cross sectional diameter of one of the first and secondpassageways.
 17. The unit fuel injector of claim 16 wherein the angle isabout 90 degrees.
 18. The unit fuel injector of claim 14 wherein thediameter of the enlarged cavity is at least twice the cross sectionaldiameter of one of the first and second passageways.
 19. The improvementof claim 1 wherein the diameter of the enlarged cavity is at least twicethe cross sectional diameter of one of the first and second passageways.